Organometallic films, methods for applying organometallic films to substrates and substrates coated with such films

ABSTRACT

Organometallic coatings or films, substrates coated with such films and methods for applying the films to the substrates are disclosed. The organometallic film or coating is derived from a transition metal compound containing both halide ligands and alkoxide ligands. Coated articles comprising polymer substrates and adhered to the substrate surface an organometallic film in which the metal comprises halide and alkoxide ligands are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from U.S. Provisional PatentApplication Ser. No. 60/859,193, filed Nov. 15, 2006.

FIELD OF THE INVENTION

The present invention relates to organometallic films, to methods ofapplying such films to surfaces of various substrates and to substratescoated with organometallic films.

BACKGROUND OF THE INVENTION

Self-assembled films or layers on various substrates are well known inthe art. These films or layers typically have functional groups (headgroups) that bond to a cofunctional group on the substrate surface andorgano groups that have some mutual attraction to neighboring moleculesin the layer(s) or to the surface. The self-assembled films are used invarious applications such as for medical and electrical use. In medicalapplications, the self-assembled films are used to form an interfaciallayer between a titanium orthopedic implant and the surrounding bodytissue. For electrical applications, the self-assembled films are usefulfor improving the performance of devices that incorporateorganic-inorganic interfaces such as those found in organiclight-emitting diodes. An example of a self-assembled organic layer isdisclosed in U.S. Pat. No. 6,645,644 in which an organometallic compoundsuch as a titanium or zirconium transition metal alkoxide is applied toa substrate such as a metal having a native oxide surface. The alkoxidegroups react with the oxide groups forming a secure surface bond. Thefree or unreacted alkoxide groups are available for reaction withreactive groups such as acid groups in a subsequently applied layer.

Unfortunately, such organometallic coatings often have poor durabilityand are easily removed from many substrates, particularly polymersubstrates such as polycarbonates and polysiloxanes.

It would be desirable to provide an organometallic coating derived froma transition metal alkoxide that has better durability and adhesion tovarious substrates, particularly polymer substrates.

SUMMARY OF THE INVENTION

The present invention provides a method of depositing an organometalliccoating to a substrate comprising:

-   -   (a) contacting the surface of the substrate with a transition        metal compound having both halide and alkoxide ligands so as to        deposit a film on the substrate,    -   (b) exposing the film to conditions sufficient to form a        polymeric metal oxide film with alkoxide and hydroxyl ligands.

The present invention also provides for organometallic films or coatingscomprising a polymeric transition metal oxide with alkoxide, hydroxylligands and halide ligands.

The present invention also provides for coated polymer substrates havingadhered to the substrate surface an organometallic film comprisingligands selected from halide and alkoxide.

The organometallic film can act as an anchor for functional coatings(e.g. hydrophobic, antifog, antistatic, conductive, etc.), or as anadhesion promoter at organic/organic, organic/inorganic interfaces (e.g.as an adhesion promoter at a polyimide/polyester interface).

DETAILED DESCRIPTION

The organometallic compound used in the method of the invention ispreferably derived from a transition metal selected from Group IIIB ofthe Periodic Table or a transition metal selected from Group IVB, VB andVIB of the Periodic Table. Preferred transition metals are titanium,zirconium, lanthanum, hafnium, tantalum and tungsten. The organo portionof the organometallic compound contains ligands comprising bothalkoxides and halides. Examples of suitable alkoxide groups are thosecontaining from 1 to 18, preferably 2 to 8 carbon atoms, such asethoxide, propoxide, isopropoxide, butoxide, isobutoxide andtert-butoxide. Examples of suitable halides are fluoride and chloride.Other ligands such as acetyl acetonates may also be present.

The organometallic compounds can be esters and polymeric forms of theesters. With reference to titanium and zirconium, examples of variouscompounds include

a. alkyl esters of titanium and zirconium having the general formula(X)_(4-y)-M(OR)_(y), wherein M is selected from Ti and Zr; X is selectedfrom fluorine and chlorine; R is C₁₋₁₈ alkyl and y=2 to 3,

b. polymeric alkyl titanates and zirconates obtainable by condensationof the alkyl esters of (a), i.e., partially hydrolyzed alkyl esters ofthe general formula RO[-M(OR)(X)O—]_(y)R, wherein M, R and X are asabove and y is a positive integer, and

c. mixtures of (a) and (b).

The organometallic compounds may be used neat and applied under vacuumby chemical vapor deposition techniques or it may be dissolved ordispersed in a diluent and applied by coating techniques describedbelow. Examples of suitable diluents are alcohols such as methanol,ethanol and propanol, aliphatic hydrocarbons, such as hexane, isooctaneand decane, ethers, for example, tetrahydrofuran and dialkylethers suchas diethylether.

Also, adjuvant materials may be present in the organometalliccomposition. Examples include stabilizers such as sterically hinderedalcohols, surfactants and anti-static agents. The adjuvants if presentare present in amounts of up to 30 percent by weight based on thenon-volatile content of the composition.

The concentration of the organometallic compound in the composition isnot particularly critical but is usually at least 0.001 millimolar,typically from 0.01 to 100 millimolar, and more typically from 0.1 to 50millimolar.

The organometallic treating composition can be obtained by mixing all ofthe components at the same time with low shear mixing or by combiningthe ingredients in several steps. The organometallic compounds arereactive with moisture, and care should be taken that moisture is notintroduced with the diluent or adjuvant materials and that mixing isconducted in a substantially anhydrous atmosphere.

Examples of substrates are those which have groups on their surface thatare reactive with functional groups associated with the organometalliccoating. Examples of such groups are oxide and/or hydroxyl groups.Non-limiting examples of such substrates are those which inherently havesuch groups on their surface or which form such groups by subsequenttreatment such as exposure to the environment or a plasma treatment.Examples of materials which form metal oxide surfaces upon exposure toambient conditions include steels, including stainless steels, iron, andmetals which acquire a non-ablating oxide coating upon exposure to theambient environment, for example, tantalum, titanium, titanium alloys,aluminum, and aluminum alloys. Additional examples of materials thatacquire an oxide layer upon exposure to the ambient conditions areceramic materials, for example, silicon nitride. Also suitable in themethod of the present invention are materials which have an oxidecoating imparted to them, for example, thick film oxide insulators insemiconducting devices, and those which can be derivatized to have anoxide surface, for example, gallium arsenide, gallium nitride, andsilicon carbide. Other examples include conducting oxides, such asindium tin oxide, deposited on a glass substrate. Also, metal oxides canbe deposited on polymer substrates, for example, “stacked” metal oxideson polymer substrates to provide anti-reflective properties. Examples ofpolymer substrates are those that contain OH or oxide groups, such asacrylic copolymers made from one or more monomers that contain hydroxylgroups. Also, composite inorganic/organic polymers such as organopolymers containing entrained silica and/or alumina may be used.Surprisingly, it has been found that certain polymers that do not adherewell to organometallic coatings such as described in the aforementionedU.S. Pat. No. 6,645,644 adhere very well to the organometallic coatingsof the present invention. Examples of such polymers are polycarbonatesincluding aromatic and aliphatic polycarbonates, polyurethanes,polyesters, polyepoxides, acrylic polymers and copolymers (withouthydroxyl groups) and polysiloxanes. The polymer can be in the form of apolymer substrate or a polymer coating on a different substrate, forexample, a metal or metal oxide with a polymer surface coating, and apolycarbonate substrate such as an ophthalmic lens with a polysiloxanehard coat on its surface.

Preferably, the polymer surface is oxidized such as by subjecting thepolymer to an atmospheric plasma treatment in the presence of air beforeapplication of the organometallic coating.

As mentioned above, the organometallic compound may be dissolved ordispersed in a diluent and applied by conventional means such asimmersion such as dipping, rolling, spraying or wiping to form a film.The transferred organometallic compound is then exposed to conditionssufficient to form a polymeric metal oxide coating in a multilayerconfiguration with unreacted alkoxide and hydroxyl groups and halidegroups. This can be accomplished by depositing the film under conditionsresulting in hydrolysis and self-condensation of the alkoxide groups.These reactions result in a polymeric coating being formed that providescohesive strength to the film. The conditions necessary for thesereactions to occur is to deposit the film in the presence of water, suchas a moisture-containing atmosphere. The resulting film should also havesome unreacted alkoxide groups and/or hydroxyl groups for reaction andpossible covalent bonding with the reactive groups on the substratesurface and with possible overlayer material. Concurrently with theself-condensation reaction, the diluent is evaporated. Depending on thereactivity of the functional groups in the organometallic compound andon the substrate surface, heating may be required to bond theorganometallic layer to the substrate. For example, temperatures of 50to 200° C. may be used. However, for readily co-reactive groups, ambienttemperatures, that is, 20° C., may be sufficient. Although not intendingto be bound by any theory, it is believed the polymeric metal oxide isof the structure:[M(O)_(x)(OH)_(y)(OR)_(z)(Q)_(w)]_(n)where M is the metal of the invention, R is an alkyl group containingfrom 1 to 30 carbon atoms; Q is a halide group; x+y+z+w=V, the valenceof M; x, y, z and w are at least 1; x=V−y−z−w; y=V−x−z−w; z=V−x−y−w;w=V−x−y−z; n is greater than 2, such as 2 to 1000.

For optical applications, the resulting film typically has a thicknessof 5 to 100 nanometers. For other applications, thicker films can beused. When the organometallic compound is used neat and applied bychemical vapor deposition techniques in the absence of moisture, a thinmetal alkoxide film is believed to form. Polymerization, if any occurs,is minimized and the film may be in monolayer configuration. When theorganometallic compound is subjected to hydrolysis and self-condensationconditions as mentioned above, thicker films with better durability areformed.

The process of the present invention can be used to provide a film orlayer that is continuous or discontinuous, that is, in a pattern on thesubstrate surface. Non-limiting examples include spraying thecomposition onto a substrate in pre-determined areas, for example, byink-jet printing or stenciling. Other methods may be found by adaptingprinting techniques, including stamping, lithographing and gravureprinting a coating solution onto the substrate in a pattern.

As mentioned above, an overlayer or a different film can be applied tothe organometallic film. Such an overlayer material preferably containsgroups that are reactive with the alkoxide and/or hydroxyl groups, suchas hydroxyl groups or acid groups or derivatives thereof.

Preferably, the overlayer is an organic acid or a derivative thereof.The acid may be a carboxylic acid, a sulfonic acid or a phosphorus acid,such as a phosphoric acid, a phosphonic acid or a phosphinic acid. Byderivatives of acids are meant functional groups that perform similarlyas acids such as acid salts, acid esters and acid complexes. The organogroup of the acid may be monomeric, oligomeric or polymeric. Forexample, the organo acid may be a monomeric, phosphoric, phosphonic orphosphinic acid.

Examples of monomeric phosphoric acids are compounds or a mixture ofcompounds having the following structure:(RO)_(x)P(O)(OR′)_(y)wherein x is 1-2, y is 1-2 and x+y=3, R is a radical having a total of1-30, preferably 6-18 carbons, where R′ is H, a metal such as an alkalimetal, for example, sodium or potassium or lower alkyl having 1 to 4carbons, such as methyl or ethyl. Preferably, a portion of R′ is H. Theorganic component of the phosphoric acid (R) can be aliphatic (e.g.,alkyl having 2-20, preferably 6-18 carbon atoms) including anunsaturated carbon chain (e.g., an olefin), or can be aryl oraryl-substituted moiety.

Example of monomeric phosphonic acids are compounds or mixture ofcompounds having the formula:

wherein x is 0-1, y is 1, z is 1-2 and x+y+z is 3. R and R″ are eachindependently a radical having a total of 1-30, preferably 6-18 carbons.R′ is H, a metal, such as an alkali metal, for example, sodium orpotassium or lower alkyl having 1-4 carbons such as methyl or ethyl.Preferably at least a portion of R′ is H. The organic component of thephosphonic acid (R and R″) can be aliphatic (e.g., alkyl having 2-20,preferably 6-18 carbon atoms) including an unsaturated carbon chain(e.g., an olefin), or can be an aryl or aryl-substituted moiety.

Example of monomeric phosphinic acids are compounds or mixture ofcompounds having the formula:

wherein x is 0-2, y is 0-2, z is 1 and x+y+z is 3. R and R″ are eachindependently radicals having a total of 1-30, preferably 6-18 carbons.R′ is H, a metal, such as an alkali metal, for example, sodium orpotassium or lower alkyl having 1-4 carbons, such as methyl or ethyl.Preferably a portion of R′ is H. The organic component of the phosphinicacid (R, R″) can be aliphatic (e.g., alkyl having 2-20, preferably 6-18carbon atoms) including an unsaturated carbon chain (e.g., an olefin),or can be an aryl or aryl-substituted moiety.

Examples of organo groups which may comprise R and R″ include long andshort chain aliphatic hydrocarbons, aromatic hydrocarbons andsubstituted aliphatic hydrocarbons and substituted aromatichydrocarbons. Examples of substituents include carboxyl such ascarboxylic acid, hydroxyl, amino, imino, amido, thio, cyano, and fluoro.

Representative of the organophosphorous acids are as follows: aminotrismethylene phosphonic acid, aminobenzylphosphonic acid, 3-aminopropyl phosphonic acid, O-aminophenyl phosphonic acid, 4-methoxyphenylphosphonic acid, aminophenylphosphonic acid, aminophosphonobutyric acid,aminopropylphosphonic acid, benzhydrylphosphonic acid, benzylphosphonicacid, butylphosphonic acid, carboxyethylphosphonic acid,diphenylphosphinic acid, dodecylphosphonic acid, ethylidenediphosphonicacid, heptadecylphosphonic acid, methylbenzylphosphonic acid,naphthylmethylphosphonic acid, octadecylphosphonic acid, octylphosphonicacid, pentylphosphonic acid, phenylphosphinic acid, phenylphosphonicacid, bis-(perfluoroheptyl) phosphinic acid, perfluorohexyl phosphonicacid, styrene phosphonic acid, dodecyl bis-1,12-phosphonic acid.

In addition to the monomeric organophosphorous acids, oligomeric orpolymeric organophosphorous acids resulting from self-condensation ofthe respective monomeric acids may be used.

To provide hydrophobic properties to the overlayer, the organo acid orderivative thereof is preferably a fluorinated material, typically aperfluorinated oligomer having a number average molecular weight of lessthan 2000. The perfluorinated material can be a perfluorinatedhydrocarbon of the following structure:R_(f)—(CH₂)_(p)—Xwhere R_(f) is a perfluorinated alkyl group or a perfluorinated alkyleneether group and p is 2 to 4, preferably 2.

Examples of perfluoroalkyl groups are those of the structure:

where Y is F or C_(n)F_(2n+1); m is 4 to 20 and n is 1 to 6.

Examples of perfluoroalkylene ether groups are those of the structure:

where A is an oxygen radical or a chemical bond; n is 1 to 6; Y is F orC_(n)F_(2n+1); b is 2 to 10; W is H, F, C_(n)H_(2n) or C_(n)F_(2n); m is0 to 6, and p is 0 to 18.

X is an acid group or an acid derivative. Preferably, X is:

where R and R″ are a hydrocarbon or substituted hydrocarbon radicalhaving up to 200, such as 1 to 30 and 6 to 20 carbons, R can alsoinclude the perfluoroalkyl groups mentioned above, and R′ is H, a metalsuch as potassium or sodium or an amine or an aliphatic radical, forexample, alkyl including substituted alkyl having 1 to 50 carbons,preferably lower alkyl having 1 to 4 carbons such as methyl or ethyl, oraryl including substituted aryl having 6 to 50 carbons.

Examples of fluorinated materials are esters of perfluorinated alcoholssuch as the alcohols of the structure:

where Y is F or C_(n)F_(2n+1); m is 4 to 20 and n is 1 to 6.

Examples of suitable esters are stearates and citrates of such alcohols.Such materials are available from E. I. du Pont de Nemours and Companyunder the trademark ZONYL FTS and ZONYL TBC.

For application to the surface of the substrate, the overlayer materialis dissolved in a liquid diluent. The concentration of the overlayermaterial is typically dilute, for example, no greater than 10 percent ona weight/volume basis for solid overlayer material and 10 percent on avolume/volume basis for oil and liquid overlayer material, andpreferably is within the range of 0.01 to 1.0 percent. The percentagesare based on total weight or volume of the solution.

Examples of suitable diluents are hydrocarbons such as hexane, isooctaneand toluene; ketones such as methyl ethyl ketone; alcohols such asmethanol and ethanol; ethers such as tetrahydrofuran. Fluorinatedsolvents such as nonafluorobutylmethyl ether and fluorinated solventsavailable as HFE-7100, supplied by 3M Innovative Products andperfluorinated ethers supplied by Solvay Solexis under the trademarkGALDEN are preferred for use with the fluorinated material. Thefluorinated solvents can be used in admixtures with the other solventsmentioned above. The fluorinated solvents or diluents are different fromthe fluorinated materials in that the fluorinated solvents or diluentsare not film formers, whereas the fluorinated materials are. Preferably,the vapor pressure of the diluent is high, permitting rapid evaporationat room temperature (20-25° C.). The overlayer material can be dissolvedeasily upon adding the overlayer material to the diluent.

The solution of the overlayer material can be applied to the surface ofthe optical article by dipping, rolling, spraying or wiping. Afterapplication of the overlayer material, the diluent is permitted toevaporate, with or without wiping during evaporation, preferably atambient temperature, or optionally by the application of heat.

The resultant layer typically is thin, having a thickness of about 100nanometers or less. The fluorinated overlayers are hydrophobic, having awater contact angle greater than 70°, typically from 75-130°. The watercontact angle can be determined using a contact angle goniometer such asa TANTEC contact angle meter Model CAM-MICRO.

EXAMPLES

The following examples show various coated articles and methods fortheir preparation in accordance with the invention. All parts are byweight unless otherwise indicated.

Example 1

A polycarbonate lens with a polysiloxane/acrylate hardcoat was firstoxidized using an electrical plasma source (Lectro-Tec) for 10 seconds.To coat the lens with an extremely thin layer of a polymeric tantalummetal oxide having alkoxide, chloride and hydroxide ligands, the lenswas dipped into a 1 g/L solution of tantalum (V) chloride in isopropanoland withdrawn at a rate of 2 cm/min. The lens was then dipped in a 0.1%solution of poly(hexafluoropropyleneoxide)-monophosphonic acid, or“p(HFPO)PA”, in 5% HFE-7100 (3M Innovative Products)/95% methanol andultrasonicated for 5 minutes. The lens was then withdrawn at a rate of 2cm/min and tested for water contact angle. The water contact angle wasdetermined using a contact angle Goniometer TANTEC Contact Angle Meter,Model CAM-MICRO. The water contact angle was 118 indicative of a veryhydrophobic coating.

Example 2

In a manner similar to Example 1, a lens was coated with a polymericmolybdenum metal oxide having isopropoxide, chloride and hydroxideligands and overcoated with p(HFPO)PA. The water contact angle was 118.

Example 3

In a manner similar to Example 1, a lens was coated with a polymericzirconium metal oxide having dipropylene alkoxide, chloride andhydroxide ligands and overcoated with p(HFPO)PA. The water contact anglewas 118.

Example 4

In a manner similar to Example 1, a lens was coated with a polymerictitanium metal oxide having dipropylene alkoxide, chloride and hydroxideligands and overcoated with p(HFPO)PA. The water contact angle was 116.

Example 5

In a manner similar to Example 1, a lens was coated with a polymerictitanium metal oxide having isopropoxide, chloride and hydroxide ligandsand overcoated with p(HFPO)PA. The water contact angle was 118.

The invention is now set forth in the following claims.

1. A method of depositing an organometallic coating to a substratecomprising: (a) contacting the surface of the substrate with a metalcompound having both halide and alkoxide ligands so as to deposit a filmon the substrate surface, (b) exposing the film to conditions sufficientto form a polymeric metal oxide with alkoxide and hydroxyl ligands; themethod being further characterized such that the substrate prior todeposition has groups on its surface that are reactive with the alkoxideand/or hydroxyl groups of the polymeric metal oxide.
 2. The method ofclaim 1 in which the halide ligand is chloride.
 3. The method of claim 1in which the film is exposed to conditions resulting in hydrolysis andself-condensation of the alkoxide group.
 4. The method of claim 3 inwhich the conditions sufficient are exposure of the film to amoisture-containing atmosphere.
 5. The method of claim 1 in which themetal is selected from Ti, Zr, La, Hf, Ta and W.
 6. The method of claim1 in which the substrate is selected from a metal, metal oxide,metalloid, polymer, ceramic and glass.
 7. The method of claim 1 in whichthe groups on the surface of the substrate prior to deposition are oxideand/or hydroxyl groups.
 8. The method of claim 7 in which the polymericmetal oxide is covalently bonded to the substrate.
 9. The method ofclaim 8 in which the covalent bond is formed through reaction of thesurface oxide and/or hydroxyl groups with alkoxide and/or hydroxylgroups associated with the polymeric metal oxide.
 10. The method ofclaim 1 which includes an additional step of applying a different filmto the polymeric metal oxide film.
 11. The method of claim 10 in whichthe different film is deposited from an organophosphorus acid.
 12. Themethod of claim 11 in which the organophosphorus acid is a phosphonicacid.